Over 3.5 million Americans experience homelessness annually. On any given day or night, more than 600,000 are homeless.

Some estimates place it much higher. Over one-third are families with children.

Many are combat veterans. America treats its own with disdain. They outlived their usefulness. They're unwanted. They're on their own out of luck back home.

Many end up jobless and homeless without help. Their American dream is nightmarish. Imagine trying to survive outside on frigid Chicago streets.

The Chicago Coalition for the Homeless (CCH) estimates over 116,000 homeless people during the 2012 - 2013 school year.

Nearly 19,000 students were affected. Around 98% are children of color.

Many Chicago homeless double-up with family or friends. Some ride Chicago Transit Authority (CTA) trains all night to stay warm.

Less fortunate ones live without shelter. Imagine it in sub-freezing weather. Imagine it in life-threatening wind chills.

Homelessness is largely an economic problem. It increased significantly since the 1980s. Federally funded low-income housing was cut. So were other vital social programs. They're being eliminated altogether incrementally.

America's most vulnerable suffer. They're increasingly on their own. Imagine struggling to survive in this environment. Imagine it on mean Chicago winter streets.

Many US cities have warming centers. Chicago's Department of Family and Support Services (DFSS) operates six. They're open when temperatures drop below freezing.

They're closed on weekend holidays unless otherwise indicated. During Chicago's extreme cold, they were open from 9:00AM until 8PM.

Chicago homeless shelters stay open 12 hours. They operate overnight. They do so from 7PM to 7AM. During Chicago's frigid cold, they remained open round-the-clock. They did for several days only.

Many homeless victims avoid shelters. One perhaps spoke for others saying: "The only thing that (homeless people) have in common is that we don't have homes."

At the same time, "some people won't come to (shelters) because of bedbugs, for sure," he added.

Some are allergic. They break out in hives. They get rashes. Others itch uncomfortably.

Numbers perishing during early January's extreme cold may never be known. Meteorologists call it an arctic "polar vortex." On January 6, a US National Weather Service spokesman said:

"The coldest temperatures in almost two decades will spread into the northern and central US today behind an Arctic cold front."

"Combined with gusty winds, these temperatures will result in life-threatening wind chill values as low as 60(F) below zero (51C below zero)."

Snow and icy sleet conditions made things worse in some areas. On January 8, NBC News said all states except Hawaii had locations recording below freezing temperatures.

On January 7, some cities experienced record lows. New York hit 4 degrees F. Doing so broke that date's previous record low. It stood for 118 years.

Philadelphia, Detroit, Baltimore, and many other US cities experienced record lows.

New York's all-time low was - 15 degrees F. It was on February 9, 1934. On January 20, 1985, Chicagoans experienced a record low - 27 degrees F.

Adequate protective clothing is essential outside. Multiple layers are important. So is warm head covering. Around 40 - 50% of body heat is lost when uncovered.

Other basic principles include clean clothes. Garments matted with dirt or grime lose insulation. Multiple layers of clothing should be loose. They trap dead air space between them. Doing so provides extra insulation.